A driver with the ride-sharing service Uber was arrested on Friday on suspicion of first-degree murder after police in Denver, Colorado said he fatally shot a passenger in his vehicle.

Michael Andre Hancock, 29, was being held without bond in the Denver County jail pending the formal filing of charges, according to jail records. It was unclear whether he had any legal representation.

According to a Denver Police Department probable cause affidavit, on Friday morning a man later identified as Hancock told a motorist on the side of a road that he had just shot a rider who tried to attack him.

Police found a sedan parked perpendicular to traffic on a ramp and a man with gunshot wounds lying on the floor board of the front passenger seat, the affidavit said.

Police said they removed a semi-automatic pistol from Hancock’s waistband, and later recovered 10 spent 40-calibre cartridges on the hard shoulder of the road. Hancock was arrested, but police did not provide and more details.

Uber said in a statement that it was “deeply troubled” by the arrest of Hancock, a contract driver with the company for nearly three years.

“Our thoughts are with the families of those involved. The driver’s access to the app has been removed, and we will continue working closely with police,” Uber said.

San Francisco-based Uber Technologies has faced criticism over its vetting of drivers.

Last November, the Colorado Public Utilities Commission fined the company US$8.9 million for allowing 57 people to drive either without a valid driving licence or having committed other offences that should have disqualified them.